Fair Value Measurements (Details 1) (USD $)			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Trucks [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Tractors [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Trailers [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Trailers [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value																			$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 28,297,000	$ 16,937,000	$ 11,132,000	$ 9,992,000	$ 16,283,000	$ 6,361,000	$ 882,000	$ 584,000
Total Losses			4,230,000	4,455,000	8,951,000	7,814,000	2,447,000	3,108,000	5,476,000	5,489,000	1,413,000	1,071,000	2,508,000	1,542,000	370,000	276,000	967,000	783,000
Fair Value Measurements (Textuals) (Abstract)
Fair value of total debt	$ 4,000,000,000	$ 3,990,000,000